Field
Apparatuses and methods consistent with the exemplary embodiments relate to a display apparatus, a light source driving apparatus and a driving method thereof. In particular, exemplary embodiments relate to a display apparatus, a light source driving apparatus, and a driving method thereof, in which a driving current for a display is controlled.
Description of the Related Art
A display apparatus performs so-called dimming to a contrast ratio of an image, in which a pulse width modulation (PWM) dimming method of adjusting duty of a current supplied to a light source, an analog dimming method of adjusting a peak value of a current, etc., may be used.
FIG. 1 shows operations of a related art PWM dimming method. FIG. 2 shows electrical and optical characteristics of the related art PWM dimming method.
In the related art PWM dimming as shown in FIG. 1, duty is changed while a current flowing in a light emitting diode (LED) and backlight, i.e., a light source 13, alternates between on and off in a certain cycle. Thus, an average value is adjusted within a PWM cycle, thereby controlling brightness of the backlight. The PWM dimming is quick to respond to a backlight current to a dimming signal, which makes minute dimming possible, and changes the backlight per frame in accordance with brightness of an image displayed on a panel. Also, as shown in FIG. 2, the brightness or power consumption is linearly proportional to the PWM dimming duty, so that circuit and optical characteristics can be easily anticipated. Accordingly, the PWM dimming method has been widely used as a typical dimming method for a light emitting diode (LED) television (TV) and the display apparatus.
In another dimming method of the related art, an analog dimming changes a level of a current to control the brightness of the backlight.
FIG. 3 shows electrical and optical characteristics of a related art analog dimming method.
As shown in FIG. 3, the related art analog dimming shows a saturation inclination in which as a current increases, a light-emission efficiency of a backlight becomes lower while a gradient of increased brightness gradually decreases. Further, as a current increases, a gradient of power consumption gradually increases while voltage applied to the backlight increases. When combining these two characteristics of the analog dimming, the power consumption rapidly increases as the brightness increases. Further, by lowering the current level, the power consumption further decreases as compared with the decrease in the brightness.
In comparison between FIG. 2 and FIG. 3, under the condition that there is a same maximum brightness, it will be understood that the power consumption decreases more in the related art analog dimming method than in the related art PWM dimming method as the brightness becomes lower. Therefore, as the brightness of the backlight is lowered, the related art analog dimming has an advantage that an optical efficiency of a light source increases and power consumption rapidly decreases. However, relationships between a current and brightness, between a current and power consumption and between brightness and power consumption are not linear, and the response of the backlight current to the analog dimming is slow. Therefore, in accordance with the brightness of the image, the related art analog dimming has a disadvantage that the brightness of the backlight cannot be changed per frame. Also, an analog signal for informing a current level supplied to the backlight has to be input to a driver in order to perform the analog dimming. Therefore, the display apparatus additionally needs a digital/analog (D/A) converter or a similar circuit. Therefore, even though the related art analog dimming has excellent efficiency and heat generation in comparison to the related art PWM dimming method, the related art analog dimming has not been used much in a present LED TV or a display apparatus.